The present invention relates generally to brushless DC motors. More particularly the invention relates to a three-phase brushless DC motor having a permanent magnet rotor and Hall effect devices for commutation of stator currents.
In a prior art three-phase brushless DC motor, Hall effect devices are each associated with each of the three stator windings to effect commutation of the winding currents. However, the operating characteristics of the Hall effect devices, particularly the DC potential at their Hall voltage electrodes, differ from one device to another. The nonuniform characteristics would result in differing winding currents and commutation intervals. Thus, the greater the number of Hall effect devices employed, the more it becomes difficult to provide uniformity to the winding currents and the commutation intervals.